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European Food Research and Technology -     

Investigation of the effect of addition of calcium stearate on the properties of low-density polyethylene/poly(ε-caprolactone) blends

Low-density polyethylene (LDPE) was blended with poly(ε-caprolactone) (PCL), prepared in proportions of 75/25, 50/50, and 25/75 (LDPE/PCL, wt/wt%). The effect of the addition of calcium stearate (CaSt) of these polymers was assessed by melting flow index, differential scanning calorimetry, tensile test, scanning electron microscopy (SEM), biodegradation in simulated soil with calcium determination, and enzymatic degradation. The addition of CaSt reduced the MFI of the PCL and of the 75/25 blend. The incorporation of 25 % of PCL slightly increased the T _m of LDPE. The tensile strength had no significant changes with the addition of CaSt and the polymers showed that they are incompatible according to this property. SEM showed poor interfacial interaction between PCL and LDPE, as well as that they are immiscible, and showed no significant changes on the morphology of the materials with the addition of CaSt. The results show that polymer samples after biodegradation in simulated soil present more calcium content than initial samples polymer. The soil analysis shows that the soil that contains the polymers submitted to thermal aging show smaller calcium content than the samples that were not aged. Lipase enzyme reinforced its specificity over PCL, and the addition of CaSt reduced the degradation of PCL and the 75/25 PCL/LDPE blend, however, it increased the rate of degradation of 50/50 and 25/75 blends.     

Effect of hybrid filler (HNTs‐phthalocyanine) on the thermal properties and flammability of diene rubber

Rubber is an essential polymer widely used in the auto‐industry. We report a method for the synthesis of zinc phtalocyanine (ZP), chloroalumino phthalocyanine (CP), and their hybrid fillers obtained by the synthesis of the two phtalocyanines in the presence of halloysite nanotubes (HNTs). The hybrid fillers were characterized by means of microscopic, thermal, and particle size measurement analysis. The effect of these fillers on the properties of diene rubbers were assessed in comparison with a physical mixture of halloysite and ZP or CP pigment. The dispersion degree of hybrid fillers inside an elastomeric matrix (rubber) was assessed with the atomic force microscopy. The influence of the hybrid fillers on the thermal and mechanical properties and flammability of butadiene‐acrylonitrile (NBR) and butadiene‐styrene (SBR) rubbers was assessed by analyzing the measurement results obtained by means of thermogravimetric analysis, differential scanning calorimetry, Zwick Tensile testing, FAA micro‐calorimeter, and oxygen index determination. We found that regardless of the spatial network structure of NBR and SBR rubbers, the incorporation of hybrid fillers into the matrix of the elastomers showed an improvement in their thermal and mechanical properties as well as a significant reduction in flammability. The improvement is attributed to the smaller size and much better dispersion of HZ and HC in relation to the particles of phthalocyanine. The colored composites of NBR rubber, containing hybrid filler (HZ or HC), showed an increase in the heat capacity compared to the uncolored samples, which can increase safety by facilitating the processes of self‐extinguishing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42593.     

Charge-Driven Self-Assembled Microspheres Hydrogel Scaffolds for Combined Drug Delivery and Photothermal Therapy of Diabetic Wounds

The treatment of diabetic wound remains a big clinical challenge. Hydrogel that can provide physical barrier and humidity displays amazing potentials for managing the diabetic wounds healing. Herein, a new charge-driven self-assembled microsphere hydrogel scaffold (SMHS) is reported based on an electric charge interaction, by combining use of black phosphorus (BP)-contained chitosan methacryloyl (CS) microspheres with positive charge and basic fibroblast growth factor-contained hyaluronic acid methacryloyl (HA) microspheres with negative charge. The weak charge attraction among microspheres gives the SMHS the injectable characteristic. Due to the existence of BP, near-infrared (NIR) irradiation has obvious effects on the degradation and drug release behaviors of SMHS. Significantly, SMHS that combines the short-term physical (photothermal) intervention and long-term chemical (drug release) intervention may be promising in spatio-temporal regulation of regenerative microenvironment. SMHS with NIR irradiation (SMHS+NIR) can promote cell proliferation, cell migration, angiogenesis and macrophage polarization. Moreover, in diabetic rat skin wounds, SMHS+NIR significantly accelerates the wound healing process by simultaneously inhibiting the inflammatory response, promoting angiogenesis and tissues remodeling. The outcome of this research not only provides a biomaterial for diabetic wounds healing, but also demonstrates a new strategy for designing novel hydrogel-based biomaterials which have the free editing and combination functions.